Process for extracting gold in arsenic-containing concentrate of gold and the equipment thereof

ABSTRACT

A method of extracting gold from arsenic gold ore concentrate, wherein increase the temperature of smelting chamber to 100-300° C. and then hold the temperature to remove the vapor and small quantity of dust in the arsenic gold ore concentrate; Under residual pressure≦50 Pa, increase the temperature of smelting chamber and crystallization chamber to 300-500° C. and then hold the temperature to remove the volatilized arsenic sulfides; Hold the temperature of crystallization chamber, increase the temperature of smelting chamber to 500-600° C. and then hold the temperature to remove the gaseous element sulfur decomposed; Increase the temperature of smelting chamber to 600-760° C. and then hold the temperature, lower the crystallization chamber temperature to 270-370° C. and then hold the temperature to get element arsenic; shutdown, lower the temperature, charge the air, take out the gold-rich slag after dearsenization, and extract fine gold using conventional method. This invention also provides devices for the above mentioned method, including induction heating equipment, smelting device, constant temperature crystallization device, automatic deslagging device with hydraulic operated furnace bottom, dust collection device, automatic temperature control device, vacuum measuring device and vacuum extraction device. Through large-scale production experiments, this invention completely solves the arsenic pollution and safety problems long existed in the dearsenization process of arsenic gold ore concentrate.

TECHNICAL FIELD

This invention concerns a method to extract gold from arsenic gold oreconcentrate, especially concerns a method to extract fine grained goldfrom arsenic sulfide gold ore concentrate; this invention also concern asystem to extract gold from arsenic gold ore concentrate.

BACKGROUND TECHNOLOGY

To extract gold from the mineral, especially the fine grained andsubmicron gold in the pyrite, arsenopyrite ore and other sulfide ores,it must first completely remove arsenic in these minerals so as toeffectively extract gold. It has been a big technical barrier in thegold production about how to completely remove the arsenic in the goldconcentrate and also not to cause environment pollution, which has beenrestricting the gold output.

Conventional dearsenization method is to conduct oxidizing roasting ofthe arsenic gold ore concentrate or gold bearing arsenopyrite ore tooxidize the arsenic in the mineral into volatilized As₂O₃ and arrive atthe purpose of dearsenization. Although this method is simple, it hasfour disadvantages: (1) In the roasting process, since some arsenic andgold generate a kind of low boiling point and volatilized arsenic andgold compound under the roasting temperature, about 900° C., thusgreatly lowering the gold recovery. The gold loss percentage is often upto 25-35%. (2) It is hard to get qualified arsenic product. Since theSb, Bi, Pb, Hg, Zn and other contaminating metals also volatilize andmix with As₂O₃ by form of oxides, As₂O₃ cannot meet the productrequirement on purity and cannot be sold. To utilize the As₂O₃byproduct, conventional method is to put As₂O₃ into normal pressureelectric heating vertical retort reducing furnace and use carbon toreduce As₂O₃ into element arsenic, involving heavy labor intensity. (3)Both oxidizing roasting process and the process reducing As₂O₃ intoelement As must deal with virulent As₂O₃. Each operation link is hard toavoid environment pollution by As₂O₃, especially even hard to assure thepersonal safety of operators. (4) It is not possible to remove arsenic.Since it is difficult to control the temperature of oxidizing roasting,some arsenic is left in the slag by form of oxide. Some arsenic turnsinto iron arsenate under high temperature and is left in the slag. Thehigher the temperature is, the higher arsenic content in the slag, whichis not favorable for gold extraction in the next step.

To overcome the above disadvantages of using the As₂O₃ as raw materialto produce element arsenic in the normal pressure reducing furnace, someresearch units made some small tests to directly extract element arsenicfrom arsenic concentrate by means of the vacuum process, such as thekilogram level test to remove arsenic from the cobalt ore in theexisting technologies (China Non-ferrous Metal Journal, Book 4 Issue 1,1993), which aimed at creating conditions for the next-step wet methodextraction of element cobalt. The test theory was to enable thermaldecomposition of the Co, Fe, Ni and As compound in the cobaltconcentrate under vacuum conditions and separate out element arsenic.The experimental conditions were: residual pressure 6-10 Pa andtemperature 1100-1200° C. But the experimental result had many problems:(1) arsenic grade cannot meet the international requirement of 99% ofarsenic and can only reach 76-92% of crude arsenic. Even the furtherdistillation was also hard to reach the product requirement and involvedhigh cost. (2) Since the smelting temperature was up to 1100-1200° C.and materials were under semi-molten state, it was difficult todischarge slag for application in industrial production. (3) The exhaustissue has not been solved. When arsenic vapor and vapor were generatedin the furnace, they would cause the splash of molten materials andproduce large quantity of dust polluting the arsenic product and hard toget qualified arsenic (4) Arsenic content in the slag was up to 10-18%,which brought not only low arsenic recovery, but also the problem offurther dearsenization requirement in the subsequent smelting sequence.Another example is some medium and small tests made by means of existinghorizontal type horizontal type rotary vacuum furnace to extract elementarsenic from arsenopyrite ore, which still has many problems and has notbeen used for industrial product till-now. Main problems are as follows:(1) The arsenic corrosion problem of rotary furnace has not been solved,leading to low furnace life and being not suitable for industrialproduction. (2) The furnace rotation generates large quantity of dust inthe process of continuous stirring of materials, which seriouslypollutes the product and is its second fatal weakness. (3) The exhaustproblem has not been solved. Under high temperature, vapor generatedfrom crystal water in materials directly enters the vacuum unit, oftenenables the impossible normal operation of vacuum pump and also leads tofailure of vacuum solenoid valve. The requirement on vacuum degreecannot be guaranteed. Sometimes, the water accumulated in the vacuumpump leads to the oxidization of pump parts and rejection of vacuumpump. These accidents happened often lead to leakage of vacuum systemand As₂O₃ pollution. (4) Due to continuous rotation of furnace shell, itis very difficult to measure the actual temperature in the rotary body.Plus, such furnace type integrates smelting chamber and crystallizationchamber in the same furnace shell. It is more difficult to controltemperature at connection between both chambers. (5) Deslagging andproduct stripping cannot be conducted at the same time. It must firstconduct product stripping and then deslagging, which greatly extends theoperating time. (6) Since the effective charging size of smeltingchamber (material chamber) of horizontal type rotary furnace is small,and must be less than half the actual size of smelting chamber,otherwise, the materials will flow out of the vent hole (i.e. charginghole) upon rotation and continuously flow into the crystallizationchamber and mix with the product. The above problems lead to the factthat the horizontal type rotary vacuum furnace cannot be used forindustrial production.

Another example is 100 g small tests made by given arsenopyrite oreunder vacuum conditions through thermal decomposition and extraction ofelement arsenic. The test ore charge is pure arsenopyrite ore. Firstly,the mineral is subject to cleaning to remove most impurities, andsubject to leaching with the Iron(III) sulfate to remove FeS₂ and othersulfides and get pure arsenopyrite ore as charging material. Althoughthe qualified element arsenic can be got, it is easy to realize forsmall tests using pure arsenopyrite ore as charging material, andindustrial production cannot meet such strict conditions. And the 100 glevel vacuum furnace has its integrated smelting chamber,crystallization chamber and dust chamber. After furnace shutdown andtemperature lowering, the particles of element arsenic are removed fromthe shell wall (crucible wall). Such tests can only show that theestablished fact of vacuum thermal decomposition and extraction ofelement arsenic.

Someone also made tests to adopt minor negative pressure operation inthe furnace and enable thermal decomposition of arsenopyrite ore andextraction of element arsenic. So-called minor negative pressure is thatthe pressure difference between inside and outside the furnace is about10 mm water columns. But the minor negative tests can also only show theestablished fact of thermal decomposition of arsenopyrite ore andextraction of element arsenic, and cannot eliminate the conditions ofgenerating As₂O₃, far away from the industrial production.

CONTENTS OF INVENTION

The purpose of this invention is to provide a method of extracting goldfrom arsenic gold ore concentrate; another purpose of this invention isto provide the system used in the method of extracting gold from arsenicgold ore concentrate.

To overcome the above defects, a method of extracting gold from arsenicgold ore concentrate provided in this invention involves following stepsin turn:

-   -   (1) Load the arsenic gold ore concentrate and iron powder into        the smelting chamber;    -   (2) Increase the temperature of smelting chamber to 100°        C.-300° C. and then hold the temperature to remove the vapor and        small quantity of dust in the material;    -   (3) Under residual pressure≦50 Pa, increase the temperature of        smelting chamber and crystallization chamber to 300-500° C. and        then hold the temperature to remove the volatilized arsenic        sulfides in the material;    -   (4) Hold the temperature of crystallization chamber at 300-500°        C., increase the temperature of smelting chamber to 500-600° C.        and then hold the temperature to remove the gaseous element        sulfur decomposed from material;    -   (5) Increase the temperature of smelting chamber to 600-760° C.        and then hold the temperature, meanwhile lower the temperature        of crystallization chamber to 270-370° C. and then hold the        temperature to let the arsenic vapor generated from material to        crystallize in the crystallization chamber and get element        arsenic and also get gold-rich slag after dearsenization at the        bottom of smelting chamber;    -   (6) Lower the temperature of smelting chamber and        crystallization chamber to below 150° C., charge the air, when        the inside and outside air pressures are basically equal, strip        arsenic and draw the gold-rich slag after dearsenization;    -   (7) Extract fine gold from the gold-rich slag got using        conventional method. Put the arsenic gold ore concentrate        material into the crucible. To restrict the discharge of element        sulfur causing polluted arsenic product, add proper quantity of        iron powder into the material to fix sulfur, i.e. Fe+S═FeS, let        the sulfur stay in the slag by form of FeS, tighten the mounting        nuts 12 of crystallization chamber, start the induction heating        equipment. When the temperature rises to 100-300° C. and then        hold the temperature, vapor generated in the mineral along with        small quantity of dust gathers into the center multi-slant-hole        collecting and exhaust pipe 9, and connect the vapor drainage        pipe 1 to the exhaust fan, enabling vapor along with small        quantity of dust to drain out of furnace through bottom        tightening screw 27 and vapor drainage pipe 1, and ensuring no        pollution of crystallization chamber and vacuum system by vapor        and dust. After the vapor is exhausted, block the vapor drainage        outlet and continue increasing temperature.

Using the induction heating equipment to increase temperatures ofsmelting chamber and crystallization chamber to 300-500° C. and thenhold the temperature, letting arsenic sulfide in material sharplyvolatilize into gaseous state (such as As₂S₂, As₄S₄, As₂S₃, etc.) andgather to the center of collecting and exhaust pipe 9 via its slant holeand continuously flow into the crystallization chamber. Now, since thetemperature of crystallization chamber is about 300-500° C., arsenicsulfide vapor cannot stay in crystallization chamber due to high vaporpressure, and continue flowing into the dust chamber, which can beexhausted regularly from the dust exhaust hole from dust collector andrecycled as a byproduct.

Hold the temperature of crystallization chamber at the above 300-500°C., increase the temperature of smelting chamber to 500-600° C. and thenhold the temperature, to let the FeS₂ decompose a S: FeS₂═FeS+S (gas),sulfur and iron powder in raw material combine into FeS, and let sulfurstay in the slag by form of FeS.

After the sulfur is completely solidified and various arsenic sulfidesare discharged into the dust chamber, continue increasing thetemperature of material to 600-760° C. Material begins sharpdecomposition and generates element arsenic vapor:FeAsS=Fes+As (gas) FeAsS₂=Fes+As (gas)+S(gas)Now, hold the temperature of smelting chamber at 600-760° C. andcrystallization chamber at 270-370° C. Due to the action of centermulti-slant-hole collecting and exhaust pipe 9, arsenic vapor at anypoint in the material may discharge into the center of exhaust pipe viathe nearest slant holes and form continuous arsenic gas flow that flowsupward into the constant temperature crystallization chamber, andcrystallize on the multi-hole crystallization plate 15 into a arsenicproduct. In the whole process of continuous entry of arsenic vapor intothe crystallization chamber, the temperature of crystallization chambermust be controlled within 270-370° C. If the temperature is too high,arsenic vapor will flow into dust chamber and no product will be got. Ifthe temperature is too low, β arsenic and γ arsenic will be got, ratherthan a arsenic product. Since below 760° C., arsenic in the concentratemay completely volatilize, and under such temperature, the low boilingpoint arsenic and gold compound cannot be generated, thus enabling goldto fully stay in the dry slag.

Shut down, lower temperature and strip product. When material iscompleted decomposed without output of arsenic vapor, adopt temperaturelowering measures for both interior and exterior shells ofcrystallization chamber. When the temperature is lowered below 150° C.,charge air into the air charging valve 11, till the zero heightdifference of mercury column of U type pressure gauge, thecrystallization chamber can be opened to strip product, draw thegold-rich slag after dearsenization and extract fine gold with thegold-rich slag got by means of conventional method.

In the above mentioned method of extracting gold from arsenic gold oreconcentrate, before material is charged into the above mentionedsmelting chamber, there is a step to crush the arsenic concentratematerial into grain size of 0.1 mm-2 mm.

In the above mentioned method of extracting gold from arsenic gold oreconcentrate, the weight of above mentioned iron powder is 2-4% ofarsenic concentrate material.

In the above mentioned method of extracting gold from arsenic gold oreconcentrate, holding time is 1-2 hours in the above step (2).

In the above mentioned method of extracting gold from arsenic gold oreconcentrate, holding time is 1-2 hours in the above step (3).

In the above mentioned method of extracting gold from arsenic gold oreconcentrate, holding time is 1-3 hours in the above step (4).

In the above mentioned method of extracting gold from arsenic gold oreconcentrate, holding time of smelting chamber and crystallizationchamber is respectively 3-7 hours in the above step (5).

In the above mentioned method of extracting gold from arsenic gold oreconcentrate, preferred temperature of smelting chamber in the above step(2) is 200-300° C., and more preferred temperature is 250-300° C.

In the above mentioned method of extracting gold from arsenic gold oreconcentrate, preferred temperature of smelting chamber in the above step(3) is 450-500° C.

In the above mentioned method of extracting gold from arsenic gold oreconcentrate, preferred temperature of crystallization chamber in theabove step (3) is 400-450° C.

In the above mentioned method of extracting gold from arsenic gold oreconcentrate, preferred temperature of smelting chamber in the above step(4) is 550-600° C.

In the above mentioned method of extracting gold from arsenic gold oreconcentrate, preferred temperature of crystallization chamber in theabove step (4) is 400-450° C.

In the above mentioned method of extracting gold from arsenic gold oreconcentrate, preferred temperature of smelting chamber in the above step(5) is 650-750° C., and more preferred temperature is 700-750° C.

In the above mentioned method of extracting gold from arsenic gold oreconcentrate, the temperature of crystallization chamber in the abovestep (5) is 300-360° C.

This invention provides a kind of system extracting gold from arsenicgold ore concentrate, including induction heating equipment, smeltingdevice, constant temperature crystallization device, automaticdeslagging device, dust collection device, automatic temperature controldevice, vacuum measuring device and vacuum extraction device. The abovementioned constant temperature crystallization device is fixed on theabove mentioned smelting device through demountable device. Its interiorsmelting chamber is connected with the crystallization chamber of theabove mentioned constant temperature crystallization device. Its bottomis connected with the above mentioned automatic deslagging device. Theabove mentioned smelting device, constant temperature crystallizationdevice and automatic deslagging device have vacuum sealing in between.The above mentioned constant temperature crystallization device isconnected with the above mentioned dust collection device through thedust collection inlet pipe. Such dust collection device is connectedwith the above mentioned vacuum extraction device through pipe equippedwith the vacuum measuring device. Inductor on the above mentionedinduction heating equipment is arranged on the above mentioned smeltingdevice. The thermal couples 5 of above mentioned automatic temperaturecontrol device are respectively mounted on the above mentioned smeltingdevice and constant temperature crystallization device.

In the above mentioned system to extract gold from arsenic gold oreconcentrate, the above mentioned smelting device consists of: crucibleformed by detachable bottom 8′, cover 26 and wall 8, vacuum furnaceshell 7 assembled outside the crucible, as well as a hollow collectingand exhaust pipe 9 vertically mounted at the center of the abovementioned crucible bottom 8′. The interior wall of the above mentionedcrucible and exterior wall of the above mentioned collecting and exhaustpipe 9 form the above mentioned smelting chamber, which connects withthe above mentioned crystallization chamber through the top of the abovementioned collecting and exhaust pipe 9. Many downward slant holes aredistributed on the wall of such collecting and exhaust pipe 9. A vapordrainage pipe 1 is also installed under such collecting and exhaust pipe9, which crosses the above mentioned crucible bottom 8′ and connectswith an exhaust fan.

In the above mentioned system to extract gold from arsenic gold oreconcentrate, the centerline of each slant hole of the above mentionedcollecting and exhaust pipe 9 and the centerline of the above mentionedcollecting and exhaust pipe 9 are in the same plane and form 20-40degree bevel with the lower end face of the above mentioned collectingand exhaust pipe 9.

In the above mentioned system to extract gold from arsenic gold oreconcentrate, the above mentioned crucible is made of corrosion proof andheat conducting material, preferably made of graphite.

In the above mentioned system to extract gold from arsenic gold oreconcentrate, the inductor of the above mentioned induction heatingequipment is of intermediate frequency inductor. Such intermediatefrequency inductor is in integral cast in the insulating materials andassembled in the vacuum furnace shell 7 outside the above mentionedcrucible. The above mentioned induction heating equipment also includesintermediate frequency power, capacitor for electric induction heatingsystem, intermediate frequency isolating transformer. The abovementioned intermediate frequency isolating transformer is connectedbetween the electric input end of the above mentioned intermediatefrequency inductor and intermediate frequency power.

In the above mentioned system to extract gold from arsenic gold oreconcentrate, the inductor of the above mentioned induction heatingequipment is of intermediate frequency inductor. Such inductor isassembled outside the above mentioned vacuum furnace shell 7. The abovementioned induction heating equipment also includes intermediatefrequency power and capacitor for electric induction heating system.

In the above mentioned system to extract gold from arsenic gold oreconcentrate, the above mentioned vacuum furnace shell 7 is made of hightemperature resistant, insulation, non-magnetoconductive, non conductingand non-leakage material, preferably made of ceramic or 4-fluorotheneplastic wire mesh.

In the above mentioned system to extract gold from arsenic gold oreconcentrate, insulating material is used to block the gap between theabove mentioned crucible wall 8 and the above mentioned vacuum furnaceshell 7.

In the above mentioned system to extract gold from arsenic gold oreconcentrate, the above mentioned constant temperature crystallizationdevice includes bottomless shell 14 and inner shell 13, many multi-holecrystallization plates 15 installed on one support as well as centerheating pipe 16 installed on the above mentioned shell 14 and extendingat the vertical direction in the center of shell. The space in the abovementioned inner shell 13 forms the above mentioned crystallizationchamber. The above mentioned inner shell 13 and support of multi-holecrystallization plate 15 are fixed together with the above mentionedshell 14 through the dismountable device.

In the above mentioned system to extract gold from arsenic gold oreconcentrate, a minor annular slit exists between the shell 14 and innershell 13 of the above mentioned constant temperature crystallizationdevice. The bottom of the above mentioned annular slit is plugged withrefractory materials.

In the above mentioned system to extract gold from arsenic gold oreconcentrate, the above mentioned automatic temperature control deviceincludes: a thermal couple 5 inserted on the crystallization chambershell 14 for measuring temperature in the crystallization chamber, athermal couples 5 inserted at the furnace bottom 6 for measuringtemperature of smelting chamber, as well as temperature controllerconnected with the above two thermal couples 5 and the above mentioned,induction heating equipment through compensation cord for respectivelycontrolling the temperature in the furnace and crystallization chamber.

In the above mentioned system to extract gold from arsenic gold oreconcentrate, the above mentioned smelting device is installed above theground through the support 24. Such smelting device also includes afurnace bottom 6 fixed with the above mentioned crucible bottom 8′; theabove mentioned automatic deslagging device includes: hopper 4, slag car3 as well as hydraulic lift 2 installed on the hopper 4. The abovementioned furnace bottom 6 is connected with vacuum furnace shell 7through top support of the hydraulic lift 2,between which the vacuumsealing strips are used for vacuum sealing. Upon lowering, suchhydraulic lift 2 can separate the above mentioned furnace bottom 6 andthe above mentioned crucible bottom 8′ from the above mentioned cruciblewall 8.

In the above mentioned system to extract gold from arsenic gold oreconcentrate, a layer of heat insulation material is arranged between theabove mentioned crucible bottom 8′ and the above mentioned furnacebottom 6.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the flow diagram of the method of extracting gold from arsenicgold ore concentrate provided in this invention.

FIG. 2 is one structural representation of the system of extracting goldfrom arsenic gold ore concentrate provided in this invention.

FIG. 3 is another structural representation of the system of extractinggold from arsenic gold ore concentrate provided in this invention.

DETAILED EMBODIMENTS

Now, further explanations on the method of extracting gold from arsenicgold ore concentrate provided in this invention and the system ofextracting gold from arsenic gold ore concentrate provided in thisinvention are given in combination with the drawings.

Please refer to one structural representation of the system ofextracting gold from arsenic gold ore concentrate provided shown in FIG.2, brief explanations on structural features and operating principle ofmajor equipment in this invention are made.

In the system of extracting gold from arsenic gold ore concentrateprovided in this invention, smelting device is connected with theconstant temperature crystallization device through bolts and nuts,between which the rubber strip is used for vacuum sealing; smeltingdevice is connected with the automatic deslagging device with hydraulicoperated furnace bottom through hydraulic lift 2; the constanttemperature crystallization device is connected with the dust collectiondevice through left flange of dust collection inlet pipe 17. “O” rubberring is used between left and right flanges for vacuum sealing; the dustcollection device is connected with the vacuum extraction device throughstainless steel pipe and solenoid valve 23; the intermediate frequencyinduction heating equipment is connected with the smelting devicethrough the inductor 10; inductor 10 and intermediate frequency heatingdevice are connected through flexible cable; the temperature controllingdevice is connected with all temperature control instruments throughthermal couples 5 and compensation flexible conductor. Thyristor iscontrolled through information feedback of thermal couples 5 toautomatically adjust power and control temperature; the pressuremeasuring device is connected with the macleod gauge and U type pressuregauge with vacuum hose and pressure sensing tube connector 20 to readthe vacuum degree.

Intermediate frequency heating part 10 is put in stainless steel vacuumfurnace shell 7 on the vacuum furnace support 24. To prevent vacuumdischarge, on the one hand, the whole intermediate frequency inductormust be cast and sealed with insulating material to prevent inductorshorted to earth. On the other hand, the intermediate frequencyisolating transformer is connected between the electric input end of theintermediate frequency inductor and intermediate frequency power tolower the intermediate frequency output voltage and further prevent thevacuum discharge in the furnace.

A hollow collecting and exhaust pipe 9 is vertically installed at thecenter of graphite crucible bottom 8′. Its top is connected with theconstant temperature crystallization device and enables the fixedconnection between multi-slant-hole collecting and exhaust pipe 9 andgraphite crucible bottom 8′. Upward slant holes are evenly distributedon the collecting and exhaust pipe. Each slant hole forms 30 degreebevel with the lower end face of collecting and exhaust pipe. The roleof these slant holes is to enable various gases generated by materialsin the furnace to gather to the center of collecting and exhaust pipe inthe shortest distance and minimum flow resistance, enter the multi-holecrystallization plate 15 of constant temperature crystallization chamberfrom the collecting and exhaust pipe, and crystallize into the arsenicproduct. The center collecting and exhaust pipe can greatly reduce theflow resistance of various gases generated by the melted materials, suchas arsenic vapor, steam, various arsenic sulfide vapors and so on, andalso minimize the arsenic content in the slag. A vapor drainage pipe 1is under such collecting and exhaust pipe 9, crosses the above mentionedgraphite crucible bottom 8′ and connects with the exhaust fan.

The automatic deslagging device with hydraulic operated furnace bottomincludes slag car 3, slag hopper 4, hydraulic lift 2 and lifting furnacebottom 6. Such lifting furnace bottom 6 is fixed with the graphitecrucible bottom 8′ through insulating material layer. The furnace bottom6 is connected with the stainless steel vacuum furnace shell 7 throughthe support of hydraulic lift 2, between which the vacuum rubber stripsare used for vacuum sealing. The hydraulic lift 2 drives the furnacebottom 6 and graphite crucible bottom 8′ to separate from the abovementioned graphite crucible wall 8. The hydraulic lift 2 upward supportssuch furnace bottom 6 to compact the vacuum rubber strips between suchfurnace bottom 6 and stainless steel vacuum furnace shell 7 and fulfillvacuum sealing. The lifting of furnace bottom arrives at the purpose ofautomatic deslagging. The reason why deslagging by means of lifting thefurnace bottom is because the smelting temperature≦760° C., anysubstances in the material are far from the melting conditions and theslag is dry and of the same flow property with the original material.

Center heating pipe 16 extending in vertical direction is installed atthe center of constant temperature crystallization chamber, on thecrystallization chamber shell 14 and shell center. Several equidistantmulti-hole crystallization plates 15 are installed at one tubularsupport. Such tubular support is also assembled outside the abovementioned center heating pipe 16. The crystallization chamber innershell 13 and multi-hole crystallization plate 15 are fixed with thecrystallization chamber external shell 14 through bolts and nuts 12.Screwing off the nut 12 can take off all multi-hole crystallizationplates and crystallization chamber inner shell so as to strip product.There is a minor annular slit between such crystallization chamber innershell 13 and external shell 14 to facilitate removing thecrystallization chamber inner shell 13. Since arsenic vapor is notallowed to enter such slit for crystallization, otherwise, it will causethe accident of blocking the inner shell 13. To prevent such accident,the spongeous refractory materials shall be properly plugged into thelower end of such annular slit.

The temperature control of smelting chamber is fulfilled by means ofthermal couples 5 installed at the lifting furnace bottom 6 forinformation feedback to the temperature controlling device on theintermediate frequency induction heating equipment. And the thyristor inthe temperature controlling device can automatically adjust theintermediate frequency voltage in the thyristor according to thefeedback information, i.e. adjusting the output power of intermediatefrequency to arrive at the purpose of temperature control. The constanttemperature crystallization chamber has dedicated and independenttemperature controlling device for temperature control. Its temperaturecontrol principle is the same as that of smelting chamber, using thermalcouples 5 installed at the crystallization chamber external shell 14 forinformation feedback. The temperature controlling device automaticallyadjusts the heating power of electric furnace heating wires wound on thecenter heating pipe 16 according to the changing information to arriveat the purpose of temperature control of crystallization chamber. Theelectric furnace heating wires on the heating pipe must be completelyisolated with the arsenic vapor from arsenic corrosion. The abovementioned tubular support plays the role of isolating the arsenic vaporfrom entry into the center heating chamber.

The constant temperature crystallization chamber external shell 14 isconnected with the dust collector shell 18 through the dust collectioninlet pipe 17. When the temperature rises to 300-500° C., variousarsenic sulfides volatilized from materials enter the dust chamber andare discharged through dust exhaust hole as byproducts.

The top of dust chamber 18 is connected into the vacuum extractionsystem with the stainless steel extraction pipe. By starting the vacuumunit 22, the whole integrated system arrives at the vacuum requirementthrough vacuum solenoid valve 23 and stainless steel extraction pipe.The air charging valve 21 can be used to carry out system chargingleakage check. The system vacuum degree can be measured by use of U typepressure gauge and macleod gauge connected on the pressure measuringpipe 20.

Please refer to another structural representation of the system ofextracting gold from arsenic gold ore concentrate provided shown in FIG.3, brief explanations on another structural features and operatingprinciple of smelting device are given below. The installationdescriptions of other devices are the same as those of FIG. 2.

It is put inside the ceramic vacuum furnace shell 7 on the vacuumfurnace support 24 and fixed with screw 13 and furnace shell fixingscrew 17. Since the tailor-made industrial ceramic furnace shell can notonly meet the requirement of no leakage under high vacuum, but also meetthe special non-magnetoconductive, non conducting, high temperatureresistant and high strength requirement required by electric magneticinduction heating, it is allowed to assemble the inductor 10 outside theindustrial ceramic furnace shell 7. Such structure can completelyeliminate the phenomenon of vacuum discharge, improve the operatingreliability of heating system, and also get rid of the intermediatefrequency isolating transformer required by conventional vacuum furnacefor preventing the vacuum discharge and save the power consumption ofisolating transformer. More significantly: in case the stainless steelis used as the vacuum furnace shell, it has to put the inductor insidethe stainless steel shell, leading to magnetic induction heating ofstainless steel shell and adding useless power consumption. Thisinvention adopts tailor-made ceramic vacuum furnace shell, whose totalpower consumption may be saved by 20-30% under the same power.

The graphite crucible wall 8, graphite crucible bottom 8′ and graphitecrucible cover 26 are installed in the ceramic vacuum furnace shell 7. Ahollow collecting and exhaust pipe 9 is vertically installed at thecenter of graphite crucible bottom 8′. Annular slit between ceramicshell and graphite crucible is plugged with insulating material 4.

Taking the arsenic sulfide gold ore concentrate as material, furtherdescriptions on this method are made through following experimentaldata: TABLE 1 Influence of Grain Size of Arsenic Sulfide Gold OreConcentrate on Arsenic Volatilization Amount Arsenic kg 650  740  796 848 volatilization %  <75%  <85% ≦91%     97% amount Grain size (mm)5-10 3-5 1-3 0.1-2 Temperature (° C.)  750 Residual pressure (Pa) 1-50Charge (kg) 2500 Distillation time (h)   4 Concentrate  35 arsenic grade(%)

It is seen from Table [1] that in the event of unchanged 5 conditionslike temperature and residual pressure, when the grain size is 0.1-2 mm,the optimum distillation effect can be got.

To show the relation between arsenic sulfide volatilization rate andtemperature, we made a test by the mini vacuum furnace. The test resultis listed in Table [2]. TABLE 2 Influence of Temperature on ArsenicSulfide Volatilization Rate Arsenic sulfide g  1  5  9.5  9.8volatilization amount %   10%   50%   95%   100% Temperature (° C.) 300400 450 500 Grain size (mm) 0.1-2 Residual pressure (Pa) 50 Charge (g)100  Distillation time (min) 30 Arsenical sulfide grade (%) 10

It is seen from Table [2] that when the temperature is at 450° C.,within 30 minutes, 95% arsenic sulfides have been volatilized. If timeis extended further, 100% will be volatilized. So, 450-500° C. is theoptimum decomposition temperature of arsenic sulfides.

To show the relation between FeS₂ decomposition and temperature, themini vacuum furnace is also used to make a test. The test result islisted in the Table [3]. TABLE 3 Relation Between FeS₂ Decomposition andTemperature Separated sulfur g  0    0.53    4.24   5.2    5.3 amount % 0    10%    80%    98%    100% Temperature 300 450  500  550  600 (°C.) Grain size (mm) 0.1-2 Residual 50 pressure (Pa) Charge (g) 100 Distillation  1 time (h) FeS grade (%) 20

It is seen from Table [3] that when the temperature is 550° C., largeamount of FeS₂ may be decomposed: FeS₂═FeS+S (gas), up to 98% at suchtemperature. If time is extended further, 100% will be decomposed. So,550-600° C. is the optimum decomposition temperature of FeS₂. TABLE 4Influence of Temperature on Arsenic Volatilization Amount Arsenic Kg 175350 700 860  volatilization %     20%     40%     80%  >98% amountTemperature (° C.) 550-600 600-650 650-700 700-750 Grain size (mm)0.1-2   Residual  1-50 pressure (Pa) Charge (g) 2500 Distillation time(h)   4 Concentrate  35 arsenic grade (%)

It is seen from Table [4] that in the event of unchanged 5 conditionslike grain size and residual pressure, when the temperature is 650-700°C., the arsenic volatilization is up to 80%; when the temperature is700-750° C., the arsenic volatilization is up to the maximum amount. Theslag now is still of dry slag without caking and melting. It keeps thegood flow property with lo the original material. Apparently, if thedistillation time is extended further, the volatilization amount willincrease.

Embodiment 1

Please refer to FIG. 1 the flow diagram of the method of extracting gold15 from arsenic gold ore concentrate provided in this invention. Crush2.5 t arsenic sulfide gold ore concentrate into 1 mm grain size and putthe same into the graphite crucible. Add 62 kg scrap iron powder to fixsulfur and enable it to stay in the slag by form of FeS. Tighten thecrystallization chamber mounting nut 12. Start the intermediatefrequency heating device.

Experimental conditions are shown as Table [5]. Increase the temperatureto 100° C. and then hold the temperature for 2 hours to remove the vaporand small quantity of dust in the arsenic sulfide gold ore concentrate.Vapor along with small quantity of dust generated from the concentrategather into the center multi-slant-hole collecting and exhaust pipe 9.Connect the vapor drainage pipe 1 to the exhaust fan to discharge vaporand small quantity of dust through furnace bottom tightening screw 27and vapor drainage pipe 1. When the vapor is drain out, block the vapordrainage hole; continue increasing the temperature to remove thevolatilized arsenic sulfides in the arsenic sulfide gold oreconcentrate, and when the temperature of smelting chamber andcrystallization chamber rises to 300° C. and then hold the temperaturefor 2 hours, letting arsenic sulfides in concentrate volatilize intogaseous state (such as As₂S₂, As₄S₄, As₂S₃, etc.) and gather to thecenter of collecting and exhaust pipe 9 via the slant holes ofcollecting and exhaust pipe, flow into the crystallization chamber, thento the dust chamber; to remove the decomposed gaseous element sulfur inthe arsenic sulfide gold ore concentrate, hold the crystallizationchamber temperature at 300° C., use the intermediate frequency heatingdevice to increase the smelting chamber temperature to 500° C. and thenhold the temperature for 2 hours. The decomposed element sulfur combineswith scrap iron powder in the raw material into FeS, letting the elementsulfur stay in the slag by form of FeS; to get element arsenic in thearsenic sulfide gold ore concentrate, continue increasing smeltingchamber temperature to 600° C. and then hold the temperature for 7hours, lower the crystallization chamber temperature to 270° C. and thenhold the temperature for 7 hours. Generated element arsenic vapor isdrained into the center of collecting and exhaust pipe from the nearestslant hole to form arsenic gas flow, which continuously flows into theconstant temperature crystallization chamber and crystallize onmulti-hole crystallization plate 15 into α arsenic product.

Adopt temperature lowering measures for both interior and exteriorshells of smelting chamber and crystallization chamber. When thetemperature is lowered below 150° C., charge air into the air chargingvalve 11, till the zero height difference of mercury column of U typepressure gauge, the crystallization chamber can be opened to stripproduct, take out the gold-rich slag after dearsenization. Theexperimental result is shown as Table[5]. The purity of arsenic productis 80% and concentrate dearsenization rate is 50%.

The known thiourea or cyanidation is used to treat the gold-rich slagafter dearsenization and extract gold. The gold recovery is up to90%-95%.

Embodiment 2

The same experimental steps as Embodiment 1 are adopted. The differencelies in that to remove the vapor and small quantity of dust in thearsenic sulfide gold ore concentrate, increase the temperature to 150°C. and then hold the temperature for 2 hours; to remove the volatilizedarsenic sulfides in the arsenic sulfide gold ore concentrate, increasethe temperature of smelting chamber and crystallization chamber to 320°C. and then hold the temperature for 2 hours; to remove the decomposedgaseous element sulfur in the arsenic sulfide gold ore concentrate,lower the crystallization chamber temperature to 300° C., and increasethe smelting chamber temperature to 530° C. and then hold thetemperature for 2 hours; to get the element arsenic in the arsenicsulfide gold ore concentrate, hold the crystallization chamber at 300°C. for 7 hours, continue increasing the smelting chamber temperature to630° C. and then hold the temperature for 7 hours. α arsenic product iscrystallized on the multi-hole crystallization plate 15. Theexperimental result is shown as Table[5]. The purity of arsenic productis 82% and coricentrate dearsenization rate is 55%.

Embodiment 3

The same experimental steps as Embodiment 1 are adopted. The differencelies in that to remove the vapor and small quantity of dust in thearsenic sulfide gold ore concentrate, increase the temperature to 200°C. and then hold the temperature for 1.5 hours; to remove thevolatilized arsenic sulfides in the arsenic sulfide gold oreconcentrate, increase the temperature of smelting chamber to 350° C.,and increase the temperature of crystallization chamber to 300° C., andthen hold the temperature for 1.5 hours; to remove the decomposedgaseous element sulfur in the arsenic sulfide gold ore concentrate,increase the crystallization chamber temperature to 320° C., increasethe temperature of smelting chamber to 570° C. and then hold thetemperature for 1.5 hours; to get the element arsenic in the arsenicsulfide gold ore concentrate, lower the crystallization chambertemperature to 300° C. and then hold the temperature for 6 hours,continue increasing the smelting chamber temperature to 650° C. and thenhold the temperature for 6 hours. α arsenic product is crystallized onthe multi-hole crystallization plate 15. The experimental result isshown as Table[5]. The purity of arsenic product is 85% and concentratedearsenization rate is 60%.

Embodiment 4

The same experimental steps as Embodiment 1 are adopted. The differencelies in that to remove the vapor and small quantity of dust in thearsenic sulfide gold ore concentrate, increase the temperature to 200°C. and then hold the temperature for 1.5 hours; to remove thevolatilized arsenic sulfides in the arsenic sulfide gold oreconcentrate, increase the temperature of smelting chamber to 400° C.,and increase the temperature of crystallization chamber to 350° C., andthen hold the temperature for 1.5 hours; to remove the decomposedgaseous element sulfur in the arsenic sulfide gold ore concentrate,increase the crystallization chamber temperature to 400° C., increasethe temperature of smelting chamber to 600° C. and then hold thetemperature for 1.5 hours; To get the element arsenic in the arsenicsulfide gold ore concentrate, lower the crystallization chambertemperature to 320° C. and then hold the temperature for 6 hours,continue increasing the smelting chamber temperature to 670° C. and thenhold the temperature for 6 hours. α arsenic product is crystallized onthe multi-hole crystallization plate 15. The experimental result isshown as Table[5 ]. The purity of arsenic product is 97% and concentratedearsenization rate is 70%.

Embodiment 5

The same experimental steps as Embodiment 1 are adopted. The differencelies in that to remove the vapor and small quantity of dust in thearsenic sulfide gold ore concentrate, increase the temperature to 230°C. and then hold the temperature for 1.3 hours; to remove thevolatilized arsenic sulfides in the arsenic sulfide gold oreconcentrate, increase the smelting chamber temperature to 400° C., andincrease the temperature of crystallization chamber to 300° C., and thenhold the temperature for 1.5 hours; to remove the decomposed gaseouselement sulfur in the arsenic sulfide gold ore concentrate, hold thecrystallization chamber temperature at 300° C., increase the smeltingchamber temperature to 570° C. and then hold the temperature for 2hours; to get the element arsenic in the arsenic sulfide gold oreconcentrate, hold the crystallization chamber temperature at 300° C. for6 hours, continue increasing the smelting chamber temperature to 680° C.and then hold the temperature for 6 hours. α arsenic product iscrystallized on the multi-hole crystallization plate 15. Theexperimental result is shown as Table [5]. The purity of arsenic productis 86% and concentrate dearsenization rate is 80%.

Embodiment 6

The same experimental steps as Embodiment 1 are adopted. The differencelies in that to remove the vapor and small quantity of dust in thearsenic sulfide gold ore concentrate, increase the temperature to 230°C. and then hold the temperature for 1 hour; to remove the volatilizedarsenic sulfides in the arsenic sulfide gold ore concentrate, increasethe smelting chamber temperature to 450° C., and increase thetemperature of lo crystallization chamber to 400° C., and then hold thetemperature for 1 hour; to remove the decomposed gaseous element sulfurin the arsenic sulfide gold ore concentrate, hold the crystallizationchamber temperature at 400° C., increase the smelting chambertemperature to 600° C. and then hold the temperature for 1 hour; to getthe element arsenic in the arsenic sulfide gold ore concentrate, lowerthe crystallization chamber temperature to 350° C. and then hold thetemperature for 5 hours, continue increasing the smelting chambertemperature to 700° C. and then hold the temperature for 5 hours. αarsenic product is crystallized on the multi-hole crystallization plate15. The experimental result is shown as Table [5]. The purity of arsenicproduct is 99% and concentrate dearsenization rate is 90%.

Embodiment 7

The same experimental steps as Embodiment 1 are adopted. The differencelies in that to remove the vapor and small quantity of dust in thearsenic sulfide gold ore concentrate, increase the temperature to 230°C. and then hold the temperature for 1.3 hours; to remove thevolatilized arsenic sulfides in the arsenic sulfide gold oreconcentrate, increase the smelting chamber temperature to 450° C., andincrease the temperature of crystallization chamber to 330° C., and thenhold the temperature for 1 hour; to remove the decomposed gaseouselement sulfur in the arsenic sulfide gold ore concentrate, increase thecrystallization chamber temperature to 450° C., increase the smeltingchamber temperature to 550° C. and then hold the temperature for 2.5hours; to get the element arsenic in the arsenic sulfide gold oreconcentrate, lower the crystallization chamber temperature to 320° C.and then hold the temperature for 4.5 hours, continue increasing thesmelting chamber temperature to 730° C. and then hold the temperaturefor 4.5 hours. α arsenic product is crystallized on the multi-holecrystallization plate 15. The experimental result is shown as Table[5].The purity of arsenic product is 99% and concentrate dearsenization rateis 94%.

Embodiment 8

The same experimental steps as Embodiment 1 are adopted. The differencelies in that to remove the vapor and small quantity of dust in thearsenic sulfide gold ore concentrate, increase the temperature to 250°C. and then hold the temperature for 1 hour; to remove the volatilizedarsenic sulfides in the arsenic sulfide gold ore concentrate, increasethe smelting chamber temperature to 500° C. , and increase thetemperature of crystallization chamber to 430° C., and then hold thetemperature for 1 hour; to remove the decomposed gaseous element sulfurin the arsenic sulfide gold ore concentrate, lower the crystallizationchamber temperature to 400° C., increase the smelting chambertemperature to 620° C. and then hold the temperature for 1 hour; to getthe element arsenic in the arsenic sulfide gold ore concentrate, lowerthe crystallization chamber temperature to 350° C. and then hold thetemperature for 5 hours, continue increasing the smelting chambertemperature to 730° C. and then hold the temperature for 6 hours. αarsenic product is crystallized on the multi-hole crystallization plate15. The experimental result is shown as Table [5]. The purity of arsenicproduct is 99% and concentrate dearsenization rate is 97%.

Embodiment 9

The same experimental steps as Embodiment 1 are adopted. The differencelies in that to remove the vapor and small quantity of dust in thearsenic sulfide gold ore concentrate, increase the temperature to 280°C. and then hold the temperature for 1 hour; to remove the volatilizedarsenic sulfides in the arsenic sulfide gold ore concentrate, increasethe smelting chamber temperature to 480° C., and increase thetemperature of crystallization chamber to 450° C., and then hold thetemperature for 1 hour; to remove the decomposed gaseous element sulfurin the arsenic sulfide gold ore concentrate, lower the crystallizationchamber temperature to 430° C., increase the smelting chambertemperature to 620° C. and then hold the temperature for 1 hour; to getthe element arsenic in the arsenic sulfide gold ore concentrate, lowerthe crystallization chamber temperature to 320° C. and then hold thetemperature for 3 hours, continue increasing the smelting chambertemperature to 750° C. and then hold the temperature for 3 hours. αarsenic product is crystallized on the multi-hole crystallization plate15. The experimental result is shown as Table [5]. The purity of arsenicproduct is 99% and concentrate dearsenization rate is 98%.

Embodiment 10

The same experimental steps as Embodiment 1 are adopted. The differencelies in that to remove the vapor and small quantity of dust in thearsenic sulfide gold ore concentrate, increase the temperature to 300°C. and then hold the temperature for 1 hour; to remove the volatilizedarsenic sulfides in the arsenic sulfide gold ore concentrate, increasethe smelting chamber temperature to 500° C., and increase thetemperature of crystallization chamber to 450° C., and then hold thetemperature for 1 hour; to remove the decomposed gaseous element sulfurin the arsenic sulfide gold ore concentrate, hold the crystallizationchamber temperature at 450° C., increase the smelting chambertemperature to 620° C. and then hold the temperature for 1 hour; to getthe element arsenic in the arsenic sulfide gold ore concentrate, lowerthe crystallization chamber temperature to 340° C. and then hold thetemperature for 3 hours, continue increasing the smelting chambertemperature to 760° C. and then hold the temperature for 3 hours, αarsenic product is crystallized on the multi-hole crystallization plate15. The experimental result is shown as Table [5]. The purity of arsenicproduct is 99% and concentrate dearsenization rate is 98%.

Embodiment 11

The same experimental steps as Embodiment 1 are adopted. The differencelies in that to remove the vapor and small quantity of dust in thearsenic sulfide gold ore concentrate, increase the temperature to 300°C. and then hold the temperature for 1 hour; to remove the volatilizedarsenic sulfides in the arsenic sulfide gold ore concentrate, increasethe smelting chamber temperature to 480° C., and increase thetemperature of crystallization chamber to 350° C., and then hold thetemperature for 1 hour; to remove the decomposed gaseous element sulfurin the arsenic sulfide gold ore concentrate, increase thecrystallization chamber temperature to 420° C., increase the smeltingchamber temperature to 580° C. and then hold the temperature for 1.8hours; to get the element arsenic in the arsenic sulfide gold oreconcentrate, lower the crystallization chamber temperature to 350° C.and then hold the temperature for 3 hours, continue increasing thesmelting chamber temperature to 750° C. and then hold the temperaturefor 3.5 hours. α arsenic product is crystallized on the multi-holecrystallization plate 15. The experimental result is shown as Table[5].The purity of arsenic product is 99% and concentrate dearsenization rateis 98%.

Industrial Practicability

This invention provides a method of extracting gold from arsenic goldore concentrate, where the atmosphere doesn't attend the chemicalreaction of materials in the furnace under vacuum condition, thusradically eliminating the condition generating virulent As₂O₃, and alsoradically eliminating the condition generating waste gas and wastewater,which is a breakthrough of gold smelting environment protectiontechnology. To extract arsenic under residual pressure≦50 Pa andtemperature 760° C. is not possible to generate the low boiling pointarsenic and gold compound. Therefore, the whole dearsenization processhas no gold volatilization loss, which effectively solves the problem oflow recovery of fine grained and submicron. Through large-scaleproduction experiments, this invention fulfills its purpose andanticipated effect.

The crucible on the smelting chamber wall in the system of extractinggold from arsenic gold ore concentrate provided in this invention ismade of corrosion resistant and heat conducting material, solving theproblem of corrosion and low furnace life of existing horizontal typerotary vacuum furnace; since this vacuum smelting device is fixedthrough support, avoiding the fatal weakness of seriously pollutingproduct due to large quantity of dust generated by material in furnacerotation, and the temperature is easily measured; a vapor drainage pipe1 connected with the exhaust fan under the collecting and exhaust pipe 9in the smelting chamber of this vacuum smelting device is installed,avoiding the problems of direct entry of steam generated from crystalwater in materials under high temperature into the vacuum unit, whichenables the impossible normal operation of vacuum pump and also thefailure of vacuum solenoid valve and being unable to guarantee therequirement on vacuum degree, and sometimes, the water accumulated inthe vacuum pump leads to the oxidization of pump parts and rejection ofvacuum pump; since the system respectively is equipped with smeltingdevice, constant temperature crystallization device, automaticdeslagging device and dust collection device, pure product can be got,enabling easy temperature control of the smelting chamber andcrystallization chamber and simultaneous deslagging and productstripping; since this system adopts the vertical structure, thusenlarging the effective charging size of smelting chamber. This systemovercomes existing problems of horizontal type rotary vacuum furnace andis suitable for industrial production. It features three functions: (1)being able to completely decompose arsenic in the arsenic gold oreconcentrate under low temperature and get the international standardelement arsenic product. (2) enabling element sulfur decomposed from thearsenic gold ore concentrate and various arsenic sulfides volatilized togather in the dust chamber where such byproduct is got. (3) The wholeprocess of gold extraction has no discharge of wastewater, waste gas andtoxic slag. TABLE 5 Steam Volatile arsenic drainage sulfide Sulfurdecomposition and dust temperature (° C.) Temperature (° C.) exhaustHolding Crystalliza- Holding Crystalliza- tempera- time Smelting tiontime Smelting tion Embodiment ture (° C.) (h) chamber chamber (h)chamber chamber 1 100 2 300 300 2 500 300 2 150 2 320 320 2 530 300 3200 1.5 350 300 1.5 570 320 4 200 1.5 400 350 1.5 600 400 5 230 1.3 400300 1.5 570 300 6 230 1 450 400 1 600 400 7 230 1.3 450 330 1 550 450 8250 1 500 430 1 620 400 9 280 1 480 450 1 620 430 10 300 1 500 450 1 620450 11 300 1 480 350 1 580 420 Temperature Temperature of of smeltingcrystallization chamber chamber for Holding generating Holding arsenicHolding Arsenic Dearseni- time arsenic time crystallization time purityzation Embodiment (h) vapor (° C.) (h) (° C.) (h) (As %) rate (%) 1 2600 7 270 7 80 50 2 2 630 7 300 7 82 55 3 1.5 650 6 300 6 85 60 4 1.5670 6 320 6 97 70 5 2 680 6 300 6 86 80 6 1 700 5 350 5 99 90 7 2.5 7304.5 320 4.5 99 94 8 1 730 5 350 5 99 97 9 1 750 3 320 3 99 98 10 1 760 3340 3 99 98 11 1.8 750 3.5 350 3.5 99 98

1. A method of extracting gold from arsenic gold ore concentrateinvolves the following steps in turn: (1) Load the arsenic gold oreconcentrate and iron powder into the smelting chamber. (2) Increase thetemperature of smelting chamber to 100° C.-300° C. and then hold thetemperature to remove the vapor and small quantity of dust in thematerial. (3) Under residual pressure≦50 Pa, increase the temperature ofsmelting chamber and crystallization chamber to 300-500° C. and thenhold the temperature to remove the volatilized arsenic sulfides in thematerial. (4) Hold the temperature of crystallization chamber at300-500° C., increase the temperature of smelting chamber to 500-600° C.and then hold the temperature to remove the gaseous element sulfurdecomposed from material. (5) Increase the temperature of smeltingchamber to 600-760° C. and then hold the temperature, meanwhile lowerthe temperature of crystallization chamber to 270-370° C. and then holdthe temperature to let the arsenic vapor generated from material tocrystallize in the crystallization chamber and get element arsenic andalso get gold-rich slag after dearsenization at the bottom of smeltingchamber. (6) Lower the temperature of smelting chamber andcrystallization chamber to below 150° C., charge the air, when theinside and outside air pressures are basically equal, strip arsenic andtake out the gold-rich slag after dearsenization. (7) Extract fine goldfrom the gold-rich slag got using conventional method.
 2. A method ofextracting gold from arsenic gold ore concentrate as mentioned in claim1, featuring that before material is charged into the above mentionedsmelting chamber, there is a step to crush the arsenic concentratematerial into grain size of 0.1 mm-2 mm.
 3. A method of extracting goldfrom arsenic gold ore concentrate as mentioned in claim 1, featuringthat the weight of above mentioned iron powder is 2-4% of arsenicconcentrate material.
 4. A method of extracting gold from arsenic goldore concentrate as mentioned in claim 1, featuring that holding time is1-2 hours in the above step (2).
 5. A method of extracting gold fromarsenic gold ore concentrate as mentioned in claim 1, featuring thatholding time is 1-2 hours in the above step (3).
 6. A method ofextracting gold from arsenic gold ore concentrate as mentioned in claim1, featuring that holding time is 1-3 hours in the above step (4).
 7. Amethod of extracting gold from arsenic gold ore concentrate as mentionedin claim 1, featuring that holding time of smelting chamber andcrystallization chamber is respectively 3-7 hours in the above step (5).8. A method of extracting gold from arsenic gold ore concentrate asmentioned in claim 1, featuring that temperature of smelting chamber inthe above mentioned step (2) is 200-300° C.
 9. A method of extractinggold from arsenic gold ore concentrate as mentioned in claim 8,featuring that temperature of smelting chamber in the above mentionedstep (2) is 250-300° C.
 10. A method of extracting gold from arsenicgold ore concentrate as mentioned in claim 1, featuring that temperatureof smelting chamber in the above mentioned step (3) is 450-500° C.
 11. Amethod of extracting gold from arsenic gold ore concentrate as mentionedin claim 1, featuring that temperature of crystallization chamber in theabove mentioned step (3) is 400-450° C.
 12. A method of extracting goldfrom arsenic gold ore concentrate as mentioned in claim 1, featuringthat temperature of smelting chamber in the above mentioned step (4) is550-600° C.
 13. A method of extracting gold from arsenic gold oreconcentrate as mentioned in claim 1, featuring that temperature ofcrystallization chamber in the above mentioned step (4) is 400-450° C.14. A method of extracting gold from arsenic gold ore concentrate asmentioned in claim 1, featuring that temperature of smelting chamber inthe above mentioned step (5) is 650-750° C.
 15. A method of extractinggold from arsenic gold ore concentrate as mentioned in claim 14,featuring that temperature of smelting chamber in the above mentionedstep (5) is 700-750° C.
 16. A method of extracting gold from arsenicgold ore concentrate as mentioned in claim 1, featuring that temperatureof crystallization chamber in the above mentioned step (5) is 300-360°C.
 17. A system of extracting gold from arsenic gold ore concentrate,its feature lies in inclusion of induction heating equipment, smeltingdevice, constant temperature crystallization device, automaticdeslagging device, dust collection device, automatic temperature controldevice, vacuum measuring device and vacuum extraction device. The abovementioned constant temperature crystallization device is fixed on theabove mentioned smelting device through demountable device. Its interiorsmelting chamber is connected with the crystallization chamber of theabove mentioned constant temperature crystallization device. Its bottomis connected with the above mentioned automatic deslagging device. Theabove mentioned smelting device, constant temperature crystallizationdevice and automatic deslagging device have vacuum sealing in between.The above mentioned constant temperature crystallization device isconnected with the above mentioned dust collection device through thedust collection inlet pipe. Such dust collection device is connectedwith the above mentioned vacuum extraction device through pipe equippedwith the vacuum measuring device. Inductor on the above mentionedinduction heating equipment is arranged on the above mentioned smeltingdevice. The thermal couples of above mentioned automatic temperaturecontrol device are respectively mounted on the above mentioned smeltingdevice and constant temperature crystallization device.
 18. A system ofextracting gold from arsenic gold ore concentrate as mentioned in claim17, featuring that the above mentioned smelting device consists of:crucible formed by detachable bottom (8′), cover (26) and wall (8),vacuum furnace shell (7) assembled outside the crucible, as well as ahollow collecting and exhaust pipe (9) vertically mounted at the centerof the above mentioned crucible bottom (8′). The interior wall of theabove mentioned crucible and exterior wall of the above mentionedcollecting and exhaust pipe (9) form the above mentioned smeltingchamber, which connects with the above mentioned crystallization chamberthrough the top of the above mentioned collecting and exhaust pipe (9).Many downward slant holes are distributed on the wall of such collectingand exhaust pipe (9). A vapor drainage pipe (1) is also installed undersuch collecting and exhaust pipe (9), which crosses the above mentionedcrucible bottom (8′) and connects with an exhaust fan.
 19. A system ofextracting gold from arsenic gold ore concentrate as mentioned in claim18, featuring that the centerline of each slant hole of the abovementioned collecting and exhaust pipe (9) and the centerline of theabove mentioned collecting and exhaust pipe (9) are in the same planeand form 20-40 degree bevel with the lower end face of the abovementioned collecting and exhaust pipe (9).
 20. A system of extractinggold from arsenic gold ore concentrate as mentioned in claim 18,featuring that the above mentioned crucible is made of corrosion proofand heat conducting material.
 21. A system of extracting gold fromarsenic gold ore concentrate as mentioned in claim 20, featuring thatthe above mentioned crucible is made of graphite.
 22. A system ofextracting gold from arsenic gold ore concentrate as mentioned in claim18, featuring that the inductor of the above mentioned induction heatingequipment is of intermediate frequency inductor. Such intermediatefrequency inductor is in integral cast in the insulating materials andassembled in the vacuum furnace shell (7) outside the above mentionedcrucible. The above mentioned induction heating equipment also includesintermediate frequency power, capacitor for electric induction heatingsystem, intermediate frequency isolating transformer. The abovementioned intermediate frequency isolating transformer is connectedbetween the electric input end of the above mentioned intermediatefrequency inductor and intermediate frequency power.
 23. A system ofextracting gold from arsenic gold ore concentrate as mentioned in claim18, featuring that the inductor of the above mentioned induction heatingequipment is of intermediate frequency inductor. Such inductor isassembled outside the above mentioned vacuum furnace shell (7). Theabove mentioned induction heating equipment also includes intermediatefrequency power and capacitor for electric induction heating system. 24.A system of extracting gold from arsenic gold ore concentrate asmentioned in claim 23, featuring that the above mentioned vacuum furnaceshell (7) is made of high temperature resistant, insulation,non-magnetoconductive, non conducting and non-leakage material.
 25. Asystem of extracting gold from arsenic gold ore concentrate as mentionedin claim 24, featuring that the above mentioned vacuum furnace shell (7)is made of ceramic or 4 -fluorothene plastic wire mesh.
 26. A system ofextracting gold from arsenic gold ore concentrate as mentioned in claim23, featuring that insulating material is used to block the gap betweenthe above mentioned crucible wall (8) and the above mentioned vacuumfurnace shell (7).
 27. A system of extracting gold from arsenic gold oreconcentrate as mentioned in claim 17, featuring that the above mentionedconstant temperature crystallization device includes bottomless shell(14) and inner shell (13), many multi-hole crystallization plates (15)installed on one support as well as center heating pipe (16) installedon the above mentioned shell (14) and extending at the verticaldirection in the center of shell. The space in the above mentioned innershell 13 forms the above mentioned crystallization chamber. The abovementioned inner shell (13) and support of multi-hole crystallizationplate (15) are fixed together with the above mentioned shell (14)through the dismountable device.
 28. A system of extracting gold fromarsenic gold ore concentrate as mentioned in claim 27, featuring that aminor annular slit exists between the shell (14) and inner shell (13) ofthe above mentioned constant temperature crystallization device. Thebottom of the above mentioned annular slit is plugged with refractorymaterials.
 29. A system of extracting gold from arsenic gold oreconcentrate as mentioned in claim 17, featuring that the above mentionedautomatic temperature control device includes: a thermal couple (5)inserted on the crystallization chamber shell (14) for measuringtemperature in the crystallization chamber, a thermal couples (5)inserted at the furnace bottom for measuring temperature of smeltingchamber, as well as temperature controller connected with the above twothermal couples (5) and the above mentioned induction heating equipmentthrough compensation cord for respectively controlling the temperaturein the furnace and crystallization chamber.
 30. A system of extractinggold from arsenic gold ore concentrate as mentioned in claim 17,featuring that the above mentioned smelting device is installed abovethe ground through support (24). Such smelting device also includes afurnace bottom (6) fixed with the above mentioned crucible bottom (8′);the above mentioned automatic deslagging device includes: hopper (4),slag car (3) as well as hydraulic lift (2) installed on the hopper. Theabove mentioned furnace bottom (6) is connected with vacuum furnaceshell (7) through top support of the hydraulic lift (2), between whichthe vacuum sealing strips are used for vacuum sealing. Upon lowering,such hydraulic lift (2) can separate the above mentioned furnace bottom(6) and the above mentioned crucible bottom (8′) from the abovementioned crucible wall (8).
 31. A system of extracting gold fromarsenic gold ore concentrate as mentioned in claim 30, featuring that alayer of heat insulation material is arranged between the abovementioned crucible bottom (8′) and the above mentioned furnace bottom(6).